1. Field of the Invention
The present invention relates to a laser unit and an activation method therefor, in particular, a laser unit provided with a preparatory function for activating the unit an activating method therefor.
2. Description of the Related Art
In a laser oscillator, a laser performance such as a laser output, the stability of the laser output, a beam shape and/or a light-focusing power of the beam, and a detector performance such as the sensitivity of a laser output detector may be depend on the temperature of an oscillator, an excitation medium, cooling water, a laser power supply and/or the laser output detector. In other words, immediately after the laser oscillator is activated in a low-temperature or high-temperature environment, the performance of the laser beam and/or the laser output detector may be different from the performance while the temperature is stable. In this case, as the temperature of each component of the oscillator is changed by heat generated by laser oscillation or a cooling function provided to the oscillator, and then the oscillator approaches a thermal equilibrium state as time advances, the laser performance may become stable.
Therefore, when the laser oscillator is activated in a low-temperature or high-temperature environment, by thermally stabilizing the temperature of each component of the oscillator in a preparation stage before the laser is used, the laser output may be stable and laser machining may be stably performed. For example, Japanese Unexamined Patent Publication (Kokai) No. 2005-251855 discloses a method for measuring the temperature of a laser unit and judging whether the preparation of the laser unit is complete or not based on the measured temperature. Also, another method for measuring the laser output during laser oscillation and judging whether the preparation is complete based on the measured output, has been proposed.
However, by using only the temperature of the laser unit, completion of the preparation of the laser unit may not be correctly judged. Also, another method for judging completion of the preparation based on the laser output during laser oscillation, may be disadvantageous when the method uses a uniform criterion such as just a comparison between the laser output and a constant value. For example, in a laser oscillator having one or more components deteriorated by aging, and the performance of which is inferior to the design performance thereof, the laser output in a stable state (or the state in which the preparation is completed) is generally lower than that of the original oscillator. Therefore, the completion of the preparation in such a laser oscillator cannot be correctly judged by using the same criterion as before the aged deterioration.